The birth of the Universe

Radio wavelengths are used to observe the very far, or the very old - that is, the birth of the very first stars in the very first galaxies. A new telescope in the desert of Western Australia is made of chicken wire and the results run through a large computer. The radio waves collected will have been travelling for 13 billion years.

Transcript

Robyn Williams: Now let me take you to the beginning of time, to the birth of the universe as we know it and the kind of cosmic apparatus you'll need to see this vision of the first stars and galaxies; chicken wire. Yes, the stuff of the farmyard shed will do, not because of cut-backs but because...well, let Professor Rachel Webster tell you what she's after.

Rachel Webster: It depends on the wavelength of the light, but most wavelengths of light will actually get soaked up by neutral hydrogen once we go far enough back in time or far enough away, whichever way you want to look at it. There are a few wavelengths of light that will come through that sort of opaque curtain, if you like, and radio wavelengths are certainly one of them, but optical wavelengths, for example, will get soaked up fairly comprehensively.

Robyn Williams: That's why you're going to radio, is it?

Rachel Webster: That's the main reason we're going to radio, yes.

Robyn Williams: And what does the theory say that you're likely to see?

Rachel Webster: Well, what we want to see is the birth of the first stars, it's really quite simple. So what will happen (and we know this must happen) is that the first stars are born, they turn on, they emit high energy photons at optical wavelengths, and then all of that neutral hydrogen is ionised and once it's ionised the universe is transparent and then we can see them. So what we're hoping to do is look back through the curtain or the veil and see those first stars being born, in the first galaxies, just beyond the reach of our biggest optical telescopes at the moment.

Robyn Williams: I see, so you know what you should be seeing. How will you go about realising it and actually looking?

Rachel Webster: At the moment this is still a theoretician's paradise, and what we're predicting is that we'll see bubbles in the neutral hydrogen, and because of the shape of those bubbles and the structure there will be a particular pattern of emission of 21-centimetre radiation which comes from neutral hydrogen. So 21 centimetres is a radio wavelength, it's quite long, so that can come through all the muck in-between us and there. So we've got to build a radio telescope to catch that radiation.

Robyn Williams: So Parkes wouldn't be good enough?

Rachel Webster: Parkes is a wonderful telescope and I've caught that radiation from nearby galaxies at Parkes, that's what I did for the last ten years, but this radiation is coming from so far away that it's red-shifted by a factor of about seven or eight, so the wavelength when it gets to us is actually seven or eight times longer, and so we're now in a regime where Parkes doesn't operate. So we've got to build a new sort of telescope. It turns out that the wavelength is so long that we don't need to build anything as complicated as Parkes.

The new telescope we're building will basically be bits of chicken wire rolled out in the desert in Western Australia with very simple what we call dipoles on the chicken wire. We're going to build hundreds of these, perhaps hopefully thousands of these in an area of a few square kilometres, and then collect all the signals and run them through a very large supercomputer which will be on the site in remote WA, which is pretty scary for those of us who have been out there. And we'll process the data on site and hopefully we're going to detect these signals.

Robyn Williams: What's scary about the place?

Rachel Webster: It's hot. It's about 300 or 400 kilometres north-east of Geraldton. It's in the shire of Murchison, and we're told reliably that there are about 120 people in an area the size of the UK.

Robyn Williams: How extraordinary! And I suppose if you're just a tourist who happens to be falling across there and you see this acreage of chicken wire...

Rachel Webster: No tourist will fall across this. We're on the back of somebody's cattle station, so it's not a place that you will fall across, it's really very, very remote. And that's of course why we're there because the wavelength or the frequency that we're looking at is in fact in the middle of the FM band, so as you might expect, if we're anywhere near people there's going to be polluting signals which we don't want, and so we're just going to go as far away from people as we can. It turns out that Western Australia is, in our opinion, the best place on Earth to do this, and so that's where we're going.

Robyn Williams: When do you start?

Rachel Webster: The fantastic news is that the West Australian government and CSIRO just signed the document for us to go on site last Friday, and so we'll be on site in two or three weeks.

Robyn Williams: Hopefully, and you can actually do your work now.

Rachel Webster: Well, we've got to build the telescope, and as with many of these university-based experiments we're doing this on a shoestring. So we will go out and build the telescope ourselves. It's pretty simple, we don't need a major contract or a major engineering firm to do this. We'll go out with our post-docs and students and we'll build it ourselves. It will take us a year or a year and a half to do that, but we'll progressively build it up over that time and put the systems in place and test it.

Robyn Williams: And how long does it take for those messages to come from 13 billion light years away? Presumably they've been travelling already and you can pick up stuff straight away.

Rachel Webster: Thirteen billion years, that's, as you said...so these will be the oldest signals from stars that we see.

Robyn Williams: Will you let me know when you've got the signal?

Rachel Webster: Look, you'll certainly hear about this because when we detect the signal...and the experiment is not trivial, so it won't just be a matter of switching it on...the data rate out of this telescope is unbelievable. We're talking about terabytes a second. We'll need a supercomputer to process the data and that will be on site out in the desert as well, so that's pretty scary.

Robyn Williams: That must be an amazing picture, actually, to travel across the desert, the wasteland, and there suddenly there's a supercomputer sitting there. It's a bit like Douglas Adams, isn't it?

Rachel Webster: It will very much be, and it will be an amazing juxtaposition of very remote WA with a really quite high tech instrument. The telescope is going on the site for the Australian candidate site for the SKA (square kilometre array), so it's part of the push by Australia, the Australian bid to get the SKA to Australia. And so this will be one of the precursor experiments that we'll run for the next five or more years.

Robyn Williams: And the SKA, the array, is going to be decided...I think it's between two countries.

Rachel Webster: That's correct. The two countries are South Africa and Australia at the current time. The decision is nominally in 2011, but it's possible that a decision may include both South Africa and Australia in the end. It's unclear at this stage exactly how it's going to pan out, and of course it's now at the political phase, so we'll just keep our fingers crossed.

Robyn Williams: And if Australia gets the nod we do have federal government commitment from the last budget when Minister Julie Bishop said the array would be funded. That was Rachel Webster, Professor of Astrophysics at the University of Melbourne.

Guests

Rachel Webster

Astrophysics School of Physics University of Melbourne Parkville Victoria Australia